How to set up discount loyalty program

in order to make customer discount depend on the amount of purchases over past three months?

Go to Settings-> Loyalty programs -> Change loyalty program -> click on the tab Loyalty rules. Add a new loyalty rule.
In the drop-down list Action select Credit on cash receipt, %; in the list Depends on select Amount; in field Date range for calculations that appears select the period For three months and set Thresholds of values of credit or discount.

How to set up discount program to make discount depend on the amount of purchases over three months.

To test the loyalty program rules go to the Web register and make a few transactions with different amount of purchases within the intervals specified in the loyalty program. You can check login and password to enter the Register under Settings -> Registers and salespeople by clicking the Edit button.